Reduction gear



R. CHILTON REDUCTION GEAR Jan. 24, 1939.

Filed July 16, 1937 INVENTOR. Roman (21117011 Patented Jan. 24, 1939 I Y1 UNITED STATES PATENT OFFICE REDUCTION GEAR Roland Chilton,'R.idgewood,N. 3., assignor, by

mesne assignments, to Wright Aeronautical Corporation, Paterson, N. J.,a corporation of New York Application July 16, 1937, Serial No. 153,906

13 Claims. (Cl. 74-305) This invention relates to planetary reductiongear tooth width to the other without making any gears, the specificembodiment of the drawing other changes in the organization.illustrating a gear suitable for a large aircraft According to thisinvention, the teeth of the engine. gears are stiffened by suitableribs'or flanges at 5 In such gears, all other proportions being the endof the teeth remote from the power ap- 5 equal, the power transmitted isproportional to plication side of the planetary carrier. In this thenumber of planet pinions that may be ernway, the tendency of the load toconcentrate at ployed. As the gear ratio approaches 2:1 the one end ofthe pinion, due to deflections in the pinions become smaller and,accordingly, a larger supporting member, is compensated by ribs of thenumber may be used giving great advantages as appropriate stiffnessplaced at the opposite ends 10 to the specific capacity of a given gearwhen the of the gears.

optimum number of pinions is utilized, provided The'actual stiffnessrequirements of these ribs always'that the load is evenly distributedover all varies with each design and is determined in of the pinions.This distribution is a question of practice by making the first gear setwith ribs of .the relationship between the inherent operating excessivedepth and reducing them as required, 15

deflections in the structure as a whole, and the after the gear has beenrun under full load conmanufacturlng tolerances in the parts. Withditions and inspected for high local tooth loads. modern productionmethods, tooth spacing errors If the stiffness of the ribs has in factbeen exare very minute and it is the accuracy of spacing aggerated in:the initial design, the high tooth 29 in the pinion bearings thatcomprises the most loading will show up, on inspection, at theunimportant item of dimensional control as to load supportedffiend ofthe pinions. Thus, the ribs distribution between the pinions. At thesame can be reduced in size until even contactappears time, as to loaddistribution across the face of the throughout the length of the pinionteeth.

teeth of any individual pinion, the deflections of Other objects andadvantages will be obvious as the pinion supporting structure are thepredomifrom, or will be pointed out, in the following dehating factor.scription with reference to the drawing in which, ,In this type of gear,the pinion supports com- Fig. 1' is a fragmentary longitudinal sectionprise cantilever Journals extending integrally through a gearincorporating the invention;

from a ring or back plate and experience has Fig. 2 is a fragmentary endsection on the shown that, if the sun and ring gears are uniline 22 ofFig. 1; and 30 iormly ri id. t se defl ti s n th supp t 00 Fis. 31s afragmentary section showing a modicentrate the tooth load at the end ofthe pinion fication to the pinions. I

. teeth next to the supported or integral end of the The drawingdiscloses a gear similar in type j ur 1. a. that nd at w ich the pow r lad is to that of my co-pending application Serial No.

applied to the pinion bearing support member. 133,153, filed March 26,1937. 35

Fortunately, the ring gears may be far from A housing shown infragmentary view at In rigid, having in fact substantial flexibility forsupports a crankshaft l2 through a bearing 14,

radial distortion under load. Further, the pinthe crankshaft having anextension IS on which ions themselves i t s yp gear are in the there issupported a propeller shaft I8 on bushform of rings supported onbearings having clearm one of which 1 shown t an 40 once, whereby thebearing load reaction is at 90 The propeller shaft is supportd on theusual around the circumference from the two i-nstanthrust bearing 22 andis provided with a large taneously loaded teeth, giving considerableinintegral flange 24 to which there is bolted a herent compensatingflexibility. The pinions pinion supporting member or Spider 26, havingshould accordingly be made as thin beneath the a large number ofintegral journals 28 extendtooth roots as is consistent with thenecessary mg leftwardly from the member 26 in Fig 1 The g f gggg zgi g'yield of gears it has journals 28 carry planet pinions 30 on floatingbeen found from experience in gears in general, bushings 32. The gearshown has a ratio of 16:9,

that zones of high tooth load are apt to be concentrated opposite to anyrib or web such as usu- Pinions as shownally connects a light gear rimto a hub, I Secured to the crankshaft. H, by splines 34,1s a actualexperiment, the zone of high tooth loading bell r g comprising a k plate36 and has followed the rib location when this has been a cylindricalring 38. A sun gear 42 having a moved, by change of design, from one endof the cylindrical portion 44 terminating in a bolting a the resultantpinion size affording room for 20 50 flange 48 is secured to a gearhousing 48 by bolts 50. 4

The principal feature of this invention resides in the location ofstiifenlng ribs or flanges I2 and M provided at the left hand end of theteeth of the ring gear 36 and of the sun gear 42 respectively. It is afurther feature of the invention that the cylindrical portions ll of thegearsare relatively long and thin so that the back plates 36 and flangeof the respective gears are remote from the teeth, whereby they havelittle effect on the radial stiffness of the gears which is,accordingly, greatest at the ends .of the teeth backed up by thestiffening ribs 52-. This provision by itself would concentrate'highbearing loads at this end of the teeth, but the cantilever deflectionsof the pinion journals 28 would by themselves concentrate the bearingload at the other end of the teeth and, by

experiment on a prototype gear,.the appropriate stiffness of the flanges52-" may be determined to balance these two tendencies with the resultthat the tooth load is evenly distributed across the tooth width,thereby utilizing the inevitable inherent flexibility of the parts tocompensate against tooth misalignment under load by having'one type ofdeflection subtract from the other, so that the parts deflect insympathy.

At the same time, the inherent flexibility of the ring gears for radialyield is used cumulatively with the inherent ring type deflections ofthe pinions to compensate for such errors in pinion Journal spacing asare within the tolerances by which the manufacture of these parts iscontrolled.

It'is intended that the proportions of the rims H-Jl be exaggerated,particularly in the case of the sun gear 42 since its cylindricalelement 44 springs from what would otherwise be its lightly loaded end,giving some inherent compensation even in the absence of the ring I. Inthecase of the ring gearji, in the absence of the stiffening rib I2, theconnecting cylindrical portion a would cause the right hand end of theteeth to be most stiiib supported which adds to the deflection eiiect ofthe journals II in causing the concentration of tooth load observed atthis end of the teeth in planetary gears not compensated as by theparticular location by stiffening rib taught by this invention. a

As indicated in Pig. 3 the stiffening flange of this invention may, ifdesired, be applied to the pinions in which case it will comprise theintegral inwardly turned element III. This embodiment may be lessdesirable than that previously described in that the rib will stiflenthe pinion against ovalizing or ring deflection to a much greater extentthan will ribs applied to the large ring gears and this pinion ovalizingcomprises one of the major sources of inherent compensation againsterrors in pinion spacing.

The reduction gear here shown is for ratios close to 2:1 andincorporates a relatively large sun gear 42 and'a large number (20) ofsmall pinions III whereby the capacity of the gear is greatly increasedwithout increasing the tooth loading intensity beyond conventionalpractice. Preferably, the pinions are on centers less than 2d apartwherein d is a pinion diameter. Likewise, to accommodate a large numberof pinions, the sun gear diameter should be not less than 4d. With theseminimum proportions, space is allowed for at least fifteen pinions. Byincreasing the sun gear diameter and by reducing it, 20 or more pinionsmay be incorporated with conthe appended claims to cover all suchmodiflca- I tions and changes.

I claim as my invention:

1. A reduction gear including pinions mounted on cantilever journals onone sideofa pinion carrier and thereby subject to angular deflectionstending to concentrate the tooth loads towardsthe support end of thepinions, a pinion engaging gear, and'a gear stiflening rim thereondisposed at the other end only of the engagement from the pinionsupport, the gear being relatively flexible at the end remote from thestiffening rim.

-2. In a planetary gear, planet pinions, a planet carrier havingcantilever Journals on which said pinions are mounted, a driving memberattached to said carrier on one side of said pinions whereby deflectionsare induced in said carrier tending to concentrate the load towards thedriving member ends of the pinions, a gear engaging said pinionscomprising a relatively thin ring, and a stiffening rib on said ringdisposed only at the ends of the gear teeth remote from the carrier.

3. In combination, 'a relatively flexible ring gear, planetary pinionsengaging said gear, a pinion carrier on which said pinions arecantilev'ered,-me'ans to drive said carrier located at one end only ofsaid pinions whereby operating deflections in the carrier tend toconcentrate the tooth loads at the carrier and of the pinion teeth, andmeans to correct said concentration comprisinga-stifleningflangeontheringgeardis posed near the other ends ofthe teeth.

4. In a gearset including meshed gears comprising supports from whichthe toothed peripheries extend as cantilevers to 'one side of respectivesupports. whereby deflections under load tend to concentrate the toothloads toward the end of the teeth nearest the supports, means forequalizing the load along the teeth comprising annular ribs onrespective gears at the anti-support ends only of the teeth thereof.

'5. In a planetary gearset comprising a bell gear,

a sun gear and a planet carrier including canti lever journals havingpinions thereon and meshing with said gears, means for distributingoperating loads uniformly along the teeth of said pinions and gearscomprising annular stiffening ribs 021' the ring and sun gears adjacentthe ends thereof opposite from the planet carrier.

6. A reduction gear comprising a planet carrier having pinions iournalied on cantilevers extending from the carrier, a ring gear and a sungear each engaging said pinions, said cantilevers being yieldable underload to an attitude of ten-- gential angulation of their axes wherebythe loads tend to concentrate at the carrier end of the pinion teeth,and means to maintain uniform tooth contact between the pinions andgears compris ing stiffening flanges on the ring andesun gears only nearthe end of the teeth opposite to the planet carrier, the ring and sungears being thereby relatively free to yield radially under load at thetooth ends thereof nearest to the planet carrier to relieve tooth loadconcentration thereat.

7. In a reduction gear in combination with a carrier having a pinionjournalled upon a cantilever extending therefrom and subject to angulardeviation under load, a gear engaging said pinion, and means on saidgear comprising a stiflening flange at the anti-carrier end thereof tocontrol the radial yield along the tooth length thereof inversely tosaid deviation, to maintain uniform tooth contact of the gear and pinionteeth when under load.

8. In a reduction gear, in combination with a carrier having a pinionJournalied upon a cantilever extending therefrom and subject to angulardeviation under load, a gear engaging said pinion, and means on saidgear to control the radial yield along the tooth length thereofinversely to said deviation, to maintain uniform tooth contact of thegear and pinion teeth when under load, said means comprising agear rimhaving a stifl integral'flange at its end farthest from the pinioncarrier and being characterized by having relatively less radialstiffness at the other end nearest the pinion carrier.

9. In a gearset, in combination, a pinion and Journal thereforrelatively stiiiiy supported at one end-and subject to angular deviationfrom the support under load whereby the tooth elements depart angularlyfrom parallelism with the unloaded journal axis, and a mating gearcharacterized by having a variant radial stiffness along the toothlength, including a gear rim relatively yieldable at that end nearestthe pinion support, the other stiffer end being substantially coplanarwith that end of the pinion having the greatest deflection.

- of the two gears.

10. Ina gear comprising a toothed rim integral with a radially resilientsleeve, the latter in turn being attached to a driving member, means foradjusting the radial stifiness of the toothed rim to a greater stiffnessat the end thereof remote from the sleeve comprising a flange integralwith said remote rim end only.

11. In ,a gearset including a pinion cantile vered from a support andmating with a gear extending from a sleeve, means for controlling theradial deflections of the sleeve gear along its tooth length inverselyof the linear deflections along the tooth length of the pinion relativeto its support, when under load, comprising a gear rim of greaterthickness at that tooth end opposite to the pinion support than at itsother end. 3

12. In combination, a gear having, normally, a

substantially uniform radial stiflness along the a stiflf support at oneend thereof, the other end of the gear being relatively free and subjectto linear deflection under load, 'a mating gear meshed therewith, saidgear being-radially resilient toward the supported end of the first gearand having a rim at its opposite end to endow the gear with radialstiflness thereat, whereby linear deviation along the first gear iscompensated by inverse radial deviation of the other gear with resultantfull length contact'between the teeth ROLAND CHILTON.

